Documentation/diff-format.txt

   1 The output format from "git-diff-index", "git-diff-tree" and
   2 "git-diff-files" are very similar.
   3
   4 These commands all compare two sets of things; what is
   5 compared differs:
   6
   7 git-diff-index <tree-ish>::
   8         compares the <tree-ish> and the files on the filesystem.
   9
  10 git-diff-index --cached <tree-ish>::
  11         compares the <tree-ish> and the index.
  12
  13 git-diff-tree [-r] <tree-ish-1> <tree-ish-2> [<pattern>...]::
  14         compares the trees named by the two arguments.
  15
  16 git-diff-files [<pattern>...]::
  17         compares the index and the files on the filesystem.
  18
  19
  20 An output line is formatted this way:
  21
  22 ------------------------------------------------
  23 in-place edit  :100644 100644 bcd1234... 0123456... M file0
  24 copy-edit      :100644 100644 abcd123... 1234567... C68 file1 file2
  25 rename-edit    :100644 100644 abcd123... 1234567... R86 file1 file3
  26 create         :000000 100644 0000000... 1234567... A file4
  27 delete         :100644 000000 1234567... 0000000... D file5
  28 unmerged       :000000 000000 0000000... 0000000... U file6
  29 ------------------------------------------------
  30
  31 That is, from the left to the right:
  32
  33 . a colon.
  34 . mode for "src"; 000000 if creation or unmerged.
  35 . a space.
  36 . mode for "dst"; 000000 if deletion or unmerged.
  37 . a space.
  38 . sha1 for "src"; 0\{40\} if creation or unmerged.
  39 . a space.
  40 . sha1 for "dst"; 0\{40\} if creation, unmerged or "look at work tree".
  41 . a space.
  42 . status, followed by optional "score" number.
  43 . a tab or a NUL when '-z' option is used.
  44 . path for "src"
  45 . a tab or a NUL when '-z' option is used; only exists for C or R.
  46 . path for "dst"; only exists for C or R.
  47 . an LF or a NUL when '-z' option is used, to terminate the record.
  48
  49 <sha1> is shown as all 0's if a file is new on the filesystem
  50 and it is out of sync with the index.
  51
  52 Example:
  53
  54 ------------------------------------------------
  55 :100644 100644 5be4a4...... 000000...... M file.c
  56 ------------------------------------------------
  57
  58 When `-z` option is not used, TAB, LF, and backslash characters
  59 in pathnames are represented as `\t`, `\n`, and `\\`,
  60 respectively.
  61
  62
  63 Generating patches with -p
  64 --------------------------
  65
  66 When "git-diff-index", "git-diff-tree", or "git-diff-files" are run
  67 with a '-p' option, they do not produce the output described above;
  68 instead they produce a patch file.
  69
  70 The patch generation can be customized at two levels.
  71
  72 1. When the environment variable 'GIT_EXTERNAL_DIFF' is not set,
  73    these commands internally invoke "diff" like this:
  74
  75       diff -L a/<path> -L b/<path> -pu <old> <new>
  76 +
  77 For added files, `/dev/null` is used for <old>.  For removed
  78 files, `/dev/null` is used for <new>
  79 +
  80 The "diff" formatting options can be customized via the
  81 environment variable 'GIT_DIFF_OPTS'.  For example, if you
  82 prefer context diff:
  83
  84       GIT_DIFF_OPTS=-c git-diff-index -p HEAD
  85
  86
  87 2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
  88    program named by it is called, instead of the diff invocation
  89    described above.
  90 +
  91 For a path that is added, removed, or modified,
  92 'GIT_EXTERNAL_DIFF' is called with 7 parameters:
  93
  94      path old-file old-hex old-mode new-file new-hex new-mode
  95 +
  96 where:
  97
  98      <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
  99                       contents of <old|new>,
 100      <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 101      <old|new>-mode:: are the octal representation of the file modes.
 102
 103 +
 104 The file parameters can point at the user's working file
 105 (e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 106 when a new file is added), or a temporary file (e.g. `old-file` in the
 107 index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 108 temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 109
 110 For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 111 parameter, <path>.
 112
 113
 114 git specific extension to diff format
 115 -------------------------------------
 116
 117 What -p option produces is slightly different from the
 118 traditional diff format.
 119
 120 1.   It is preceded with a "git diff" header, that looks like
 121      this:
 122
 123      diff --git a/file1 b/file2
 124 +
 125 The `a/` and `b/` filenames are the same unless rename/copy is
 126 involved.  Especially, even for a creation or a deletion,
 127 `/dev/null` is _not_ used in place of `a/` or `b/` filenames.
 128 +
 129 When rename/copy is involved, `file1` and `file2` show the
 130 name of the source file of the rename/copy and the name of
 131 the file that rename/copy produces, respectively.
 132
 133 2.   It is followed by one or more extended header lines:
 134
 135        old mode <mode>
 136        new mode <mode>
 137        deleted file mode <mode>
 138        new file mode <mode>
 139        copy from <path>
 140        copy to <path>
 141        rename from <path>
 142        rename to <path>
 143        similarity index <number>
 144        dissimilarity index <number>
 145        index <hash>..<hash> <mode>
 146
 147 3.  TAB, LF, double quote and backslash characters in pathnames
 148     are represented as `\t`, `\n`, `\"` and `\\`, respectively.
 149     If there is need for such substitution then the whole
 150     pathname is put in double quotes.
 151
 152
 153 combined diff format
 154 --------------------
 155
 156 git-diff-tree and git-diff-files can take '-c' or '--cc' option
 157 to produce 'combined diff', which looks like this:
 158
 159 ------------
 160 diff --combined describe.c
 161 index fabadb8,cc95eb0..4866510
 162 --- a/describe.c
 163 +++ b/describe.c
 164 @@@ -98,20 -98,12 +98,20 @@@
 165         return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
 166   }
 167
 168 - static void describe(char *arg)
 169  -static void describe(struct commit *cmit, int last_one)
 170 ++static void describe(char *arg, int last_one)
 171   {
 172  +      unsigned char sha1[20];
 173  +      struct commit *cmit;
 174         struct commit_list *list;
 175         static int initialized = 0;
 176         struct commit_name *n;
 177
 178  +      if (get_sha1(arg, sha1) < 0)
 179  +              usage(describe_usage);
 180  +      cmit = lookup_commit_reference(sha1);
 181  +      if (!cmit)
 182  +              usage(describe_usage);
 183  +
 184         if (!initialized) {
 185                 initialized = 1;
 186                 for_each_ref(get_name);
 187 ------------
 188
 189 1.   It is preceded with a "git diff" header, that looks like
 190      this (when '-c' option is used):
 191
 192        diff --combined file
 193 +
 194 or like this (when '--cc' option is used):
 195
 196        diff --c file
 197
 198 2.   It is followed by one or more extended header lines
 199      (this example shows a merge with two parents):
 200
 201        index <hash>,<hash>..<hash>
 202        mode <mode>,<mode>..<mode>
 203        new file mode <mode>
 204        deleted file mode <mode>,<mode>
 205 +
 206 The `mode <mode>,<mode>..<mode>` line appears only if at least one of
 207 the <mode> is diferent from the rest. Extended headers with
 208 information about detected contents movement (renames and
 209 copying detection) are designed to work with diff of two
 210 <tree-ish> and are not used by combined diff format.
 211
 212 3.   It is followed by two-line from-file/to-file header
 213
 214        --- a/file
 215        +++ b/file
 216 +
 217 Similar to two-line header for traditional 'unified' diff
 218 format, `/dev/null` is used to signal created or deleted
 219 files.
 220
 221 4.   Chunk header format is modified to prevent people from
 222      accidentally feeding it to `patch -p1`. Combined diff format
 223      was created for review of merge commit changes, and was not
 224      meant for apply. The change is similar to the change in the
 225      extended 'index' header:
 226
 227        @@@ <from-file-range> <from-file-range> <to-file-range> @@@
 228 +
 229 There are (number of parents + 1) `@` characters in the chunk
 230 header for combined diff format.
 231
 232 Unlike the traditional 'unified' diff format, which shows two
 233 files A and B with a single column that has `-` (minus --
 234 appears in A but removed in B), `+` (plus -- missing in A but
 235 added to B), or `" "` (space -- unchanged) prefix, this format
 236 compares two or more files file1, file2,... with one file X, and
 237 shows how X differs from each of fileN.  One column for each of
 238 fileN is prepended to the output line to note how X's line is
 239 different from it.
 240
 241 A `-` character in the column N means that the line appears in
 242 fileN but it does not appear in the result.  A `+` character
 243 in the column N means that the line appears in the last file,
 244 and fileN does not have that line (in other words, the line was
 245 added, from the point of view of that parent).
 246
 247 In the above example output, the function signature was changed
 248 from both files (hence two `-` removals from both file1 and
 249 file2, plus `++` to mean one line that was added does not appear
 250 in either file1 nor file2).  Also two other lines are the same
 251 from file1 but do not appear in file2 (hence prefixed with ` +`).
 252
 253 When shown by `git diff-tree -c`, it compares the parents of a
 254 merge commit with the merge result (i.e. file1..fileN are the
 255 parents).  When shown by `git diff-files -c`, it compares the
 256 two unresolved merge parents with the working tree file
 257 (i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka
 258 "their version").
 259